The present invention relates to an image sensing apparatus for inputting images into computers and, more particularly, to an image sensing apparatus which directly controls various functions for inputting images using a computer.
An apparatus which inputs a picked-up images and makes realize desk top publishing (DTP) and a visual telephone by using a computer has become common. Accordingly, the conventional apparatus has a configuration as shown in FIG. 18 in order to input a sensed image into the computer.
In FIG. 18, reference numeral 400 denotes a conventional video camera as an image sensing device whose block diagram is shown in the figure, and reference numeral 420 denotes a video input board included in a computer (not shown). The image sensing device 400 and the video input board 420 are connected via a video cable 410, and the video input board 420 receives and processes a composite video signal which is outputted from the image sensing device 400.
First, the image sensing device 400 converts a sensed image into an electrical image signal after focusing the image using an optical lens 101P and passing through an iris diaphragm (shutter) 102P on a photo sensor of a CCD 103P. A camera controller 401 controls a motor driver 106P and a driving circuit 107P, thereby changing zooming ratio, iris, shutter speed, and so on, of the lens 101P and the shutter 102P. Further, timing signal for driving the CCD 103 is generated by a timing signal generator 108P.
The electrical image signal obtained at the CCD 103P is a color signal corresponding to a color separation access (not shown) provided in front of the CCD 103P, and a signal processor 402 applies various processes to the electrical image signal, thereby converts it into a luminance signal and a color difference signal. A color separation filter, which is made of small-sized color filters for, say, Cy, Mg, G, and Ye, is so arranged repeatedly in a predetermined order, that each pixel corresponds to each color filter. The luminance signal and the color difference signal are converted into composite video signals by a known encoder 160P, further inputted to the video input board 420. A known decoder 421 in the video input board 420 decodes the inputted composite video signals, thus reproduces the luminance signal and the color difference signal. The luminance signal and the color difference signal, outputted from the decoder 421 is inputted into memory 156P in accordance with control by a memory controller 157P.
The video input board 420 is constructed as an expansion board to be built in a computer, and connected to the computer via computer bus 155P. The computer bus 155P known as ISA Bus, VL Bus, Nu Bus, or the like, includes address lines, data lines, an interruption line, a clock, a read signal, a write signal, power supply, signal ground, and so on. Reference numeral 422 denotes a bus controller which is constructed so as to control the memory controller 157P by reading and interpreting data from the data bus when the video input board 420 is selected, which can be determined by decoding the address signal on the address line of the computer bus 155P. The memory 156P is connected to the computer bus 155P, and the image data stored in the memory 156P is transmitted to the data lines of the computer bus 155P in accordance with control by the memory controller 157P. Thus, a main CPU of the computer can receive the image data and store it in a storage medium, such as a hard disk.
Further, regarding automatic focus, a method is known to focus on an object, by detecting distinction of a display by analyzing an image signal of the object, and by controlling positions of the lens so that the distinction becomes maximum. The distinction is evaluated by using intensity of high frequency component, extracted by using a band-pass filter, of an image signal, or intensity of detection of blurring width, extracted by using a differential circuit, of the image signal. The intensity of the detected blurring width is low when the object is not properly focused, however, it increases as the object becomes better focused, and reaches the maximum value when the object is perfectly focused.
Further, in order to minimize the size of a camera, a conventional camera adopts a group of lenses of a rear focusing type, in which a focusing is achieved by moving a focus compensation lens. FIG. 11 shows examples of graphs representing cam loci. As shown in FIG. 11, relationship between the positions of a zoom lens and a focus compensation lens is not linear, thus, in order to achieve smooth zooming operation, it is necessary to make a table representing the cam locus and calculate the position of the focus compensation lens based on the speed of zooming and the position of the zoom lens. The cam loci stored in the table are inherent to a group of camera lenses.
In order to focus smoothly and at high speed during zooming operation, the focus compensation lens is moved in accordance with the cam locus. Furthermore, in order that the cam locus suitable for a distance to an object is automatically selected, the focus compensation lens is moved in accordance with the cam locus corresponding to the position and speed of the zoom lens, and to the distance to the object, which is based on the calculation performed by referring to the distinction and the cam locus table.
In addition, as "teleconference" has become common recently, several modifications of a tiltable pan head for a video camera used for the teleconference can be suggested.
For example, a construction in which a rotating part of the pan head has coaxial configuration with a single conductor and electrical transmission and reception between a base and the pan head is performed via the coaxial configuration, eliminates interference of wirings provided between the pan head and the base. Thereby the pan head can move freely without limiting its angular movement.
However, in a case where a video camera is used as an image sensing device as described above, an image signal obtained from the CCD is converted into a composite video signal once, then inputted into the video input board. The signal is then decoded and converted into each signal for Y (luminance signal), R-Y, B-Y (color difference signals), and stored in the memory. Therefore, quality of the image is deteriorated comparing to an image reproduced by directly converting a signal read by the CCD into Y, R-Y, and B-Y signal. Further, cost to manufacture the apparatus is higher since the apparatus requires complicated circuit comparing to an apparatus which reproduces an image by directly converting a signal read by the CCD into Y, R-Y, and B-Y signal.
In a case where lenses of a camera are changed, since cam loci differ from lenses to lenses, a cam locus which suits a lens newly attached to the camera can not be used, thus only distinction of an object can be used for determining whether automatic focusing is appropriate. In that case, since characteristics of cam loci are not linear, it takes considerable time to find focusing position of lenses, and zooming operation can not be carried at high speed.
Further, when a cam locus table is used, it is necessary for a camera control circuit to have cam locus tables, each of which is suitable to each attached lens. This requires an image signal processor to have a large memory area. However, the number of tables which can be stored in the memory area is limited, therefore, many kinds of camera heads having different configuration can not be used.
In a case of the aforesaid video camera for teleconference, it is required that the angular speed of the pan head should be increased even the limitation on the rotationable angle of the pan head is freed.
This is very important to design such system that detects verbal sound of a speaker and pans the video camera to pick up the image of a speaker as soon as possible, when a plurality of attendants are in a conference room sitting around a table where a video camera is set in the center of the table.
In order to improve the angular speed of the pan head, there are considered to:
1) Strengthen power of a driving motor for rotating the pan head;
2) Modify the rotating structure of the pan head; and
3) Reduce the weight of the upper portion of the pan head.